Method of producing compounds enriched in oxygen-18

ABSTRACT

A method of increasing the oyxgen-18 concentration in a compound containing oxygen and nitrogen comprising irradiating KNO3 with high energy radiation until at least 10 mole percent of said KNO3 is decomposed into KNO2 and oyxgen and separating the resulting oxygen-18 enriched KNO2 from the KNO3.

United States Patent Inventors Everett R. Johnson Chevy Chase, Md.; Edwin N. Ladov, Maple Shade, NJ. Appl. No. 874,031 Filed Nov. 4, 1969 Patented Nov. 23, 1971 Assignee The United States of America as represented by the United States Atomic Energy Commission METHOD OF PRODUCING COMPOUNDS [50] FieldofSearch 204/1571 H References Cited OTHER REFERENCES Cunningham,.lour. Phy. Chem. 65 196i pp. 628-635 Primary Examiner-Howard S. Williams Attorney-Roland A. Anderson METHOD OF PRODUCING COMPOUNDS ENRICI-IED IN OXYGENJ 8 BACKGROUND OF THE INVENTION This invention was made in the course of, or under, a contract with the United States Atomic Energy Commission.

Our invention relates to methods of altering the isotopic composition of oxygen in oxygen-containing compounds, and more specifically to methods of changing the concentration of oxygen- 1 8 in oxides of nitrogen.

One isotopic separation process uses low-temperature distillation of NO to produce "N, O, and "O. One problem associated with this process is that of obtaining pure NO feed free from N and NO, and special steps must be incorporated into a process to remove these impurities. It would be advantageous to furnish NO enriched in one of the desirable product isotopes such as *0.

SUMMARY OF THE INVENTION It is accordingly one object of our invention to provide a method of increasing the oxygen-l8 content of an oxide of nitrogen.

It is another object to provide a method of making substantially pure NO enriched in oxygen- 1 8.

Other objects of our invention will become apparent from the following description and the attached claims.

In accordance with our invention we have provided a method of changing the isotopic concentration of oxygen-l8 in an oxide of nitrogen comprising irradiating KNO, containing oxygenl 8 and oxygen-l6 until at least 10 mole percent of said KNO is converted into KNO and O, and separating the resulting oxygen- 1 8 rich KNO from the I(NO and 0,.

While KNO has previously been irradiated with high-energy radiation converting KNO into oxygen-l8 enriched KNO (see .I. Cunningham, J. Phy. Chem. 65, 628 (1961)), no isotopic efiect was found beyond 1 percent decomposition of KNO In view of the significant cost involved in the separation of KNO KNO mixture after irradiation, a practicable process for separating oxygen isotopes requires than an isotopic effect exist to a much higher decomposition level than 1 percent, i.e., to at least 10 percent. We have unexpectedly discovered that the isotopic effect in irradiating KNO exists not only beyond I percent decomposition but in fact exists to greater than l0 percent and probably to 70 percent decomposition of the KNO DESCRIPTION OF THE INVENTION In carrying out our invention a mass of KNO is subjected to penetrating radiation, until at least 10 percent of the KNO is decomposed. The radiation dose required to reach this decomposition level is about 1,000 megarads.

The KNO is preferably as pure as possible to simplify sub sequent separation steps and to minimize nonproductive sorption or radiation.

The source of radiation may be any beta, gamma, X-rays, or alpha particles source. The extent of decomposition of KNO is directly proportional to the total absorbed dose. and is not dependent on irradiation rate.

The degree of enrichment of oxygen- 1 8 in the KNO, produced ranges from a low of 1.06 at a low radiation dose, i.e., [-2 megarads to a high of 1.18 at a radiation dose of about 8 megarads, tapering off to a level of 1.09 at radiation levels of about megarads and greater.

The temperature at which our process is carried out is not critical and it may suitably range from l98 C. to about the melting temperature of KNO For reasons of economics an irradiation dose of from 1,000 to 2,000 megarads which decomposes 10 to 20 percent of the KNO is preferred.

The irradiated mass is processed to separate the oxygen- 1 8 rich KNO, from the KNO The most direct method of separating the KNO, is by fractional crystallization. The

resulting KNO, can be oxidized to KNo and the irradiation step repeated to further ennch the KNO in oxygen-l8. Each EXAMPLE Ten grams of normally enriched KNO i.e., containing 0.204 percent '0, is irradiated to a level of 1,100 megarads with a cobalt-60 source. The resulting KNO weighing approximately l gram, is separated from the KNO by fractional crystallization at 0 C. The 0 concentration in the KNO is 0.229 percent. The KNO is decomposed to give N0 which is oxidized (thermally) with gaseous oxygen enriched in oxygenl8 to KNO The resulting KNO; is irradiated to about l,l00 megarads. The KNO, formed is separated out and decomposed to NO. The NO formed in this process may be used as a feed in a low-temperature distillation process for separation of nitrogen isotopes as well as for forming oxygen-l8 enriched KNO What is claimed is:

l. A method of increasing the oxygen-l8 concentration in a compound containing oxygen and nitrogen comprising irradiating a mass of KNO with high-energy radiation to an irradiation dosage sufficient to convert at least 10 percent of said KNO to KNO and separating the resulting 0 enriched KNO, from the irradiated mass.

2. The method of claim 1 wherein the mass of KNO is irradiated to a dosage of at least 1,000 megarads.

3. The method of claim I wherein the mass of KNO is irradiated to a dosage of 1,000 to 2,000 megarads.

4. The method of claim 1 wherein the "0 enriched KNO is oxidized to KNO and the resulting KNO is irradiated to produce KNO further enriched in 0.

5. The method of claim 1 wherein the "0 enriched KNO, is decomposed to form O enriched NO. 

2. The method of claim 1 wherein the mass of KNO3 is irradiated to a dosage of at least 1,000 megarads.
 3. The method of claim 1 wherein the mass of KNO3 is irradiated to a dosage of 1,000 to 2,000 megarads.
 4. The method of claim 1 wherein the 18O enriched KNO2 is oxidized to KNO3 and the resulting KNO3 is irradiated to produce KNO2 further enriched in 18O.
 5. The method of claim 1 wherein the 18O enriched KNO2 is decomposed to form 18O enriched NO. 